Discharge electrode



y 1950 A. F. MEsToN DISCHARGE ELECTRODE 2 Sheets-Sheet 1 Filed Octl 51,1946 IN V EN TOR. Arch/bald F. Me .slon

y 1950 A. F. MESTON 2,505,907

DISCHARGE ELECTRODE Filed 001',- 51, 1946 v 2 Sheets-Sheet 2 INVEN TOR.

Archzlba/d F. Median JMY W W fiatented May 2, 1950 UNITED STATES PATENTOFFICE DISCHARGE ELECTRODE Archibald Meston, Bound: Brook, N. Jassignoz" to Research Corporation, New York, N.. Y., a corporationof NewYork Application October 31, 1946, Serial No.*-707,=006

11- Claims.

2.The present invention'relates. to a discharge electrode for apparatus.usefulin electrically removing suspendedparticles from'gases and to aprocess and apparatus for. making such electrodes. It isespeciallytadapted tow providing electrical .precipitators twith prongedstifi electrodes .which may be supported atone end only. ElectricalLprecipitators or". the type; commonly called Cottrell rprecipitatorscomprise at least two complementary electrodes one of which isanextended surface electrode upon which the precipitated particles arecollected and another. is a socalled discharge.electrode with points,prongs,

-or. sharp edges from which non-disruptive dis- :chargesemanate when astrong electric field ter- .minates uponthem. It is advantageous undersome conditions to make the discharge electrode stiff so that it.remainsinalignment adjacent to .the collecting electrode while beingsupported at one end only. Such electrodes are of course, of i moresubstantial construction. than the flexible wires, small rods,.or strips:that are in common use as discharge electrodes. .Many of the stiffelectrodes in use at the present time are obtained only at considerablecost due to the multiplicity of parts andthe careful workmanshiprequiredin their manufacture.

It is a principal object of the invention to provide a stiff electrodeof the type identified above made of materials and parts which can bereadily .obtained and easily fabricated at low cost.

object of the invention is to provide a discharge electrode havingelectric discharge elements integral therewith.

Another object of the invention is to provide a discharge electrodecomprising a stiit supporting member and an extendedrelatively flexible..,member. havingelectric discharge elementsxintegral therewith, theelectrode being character- .ized by novel fastening means for Joiningthetwo members thus permitting ready joining or separation of themembers.

i Itis an object of the invention to provide a stiff discharge electrodefor electricalprecipitators which has but few parts and which canthrough simple changes in the fabrication and/or 1 manipulationof theparts be altered in its electrical discharge characteristics. mentionedcan be made throughout the length of the electrode or. can-be madelocally so as to l provide different electrical characteristics atdif-.ferent locations along the length of the eleca trode.

The changes A further objectis to provide a dlscharge:electrodelhavinga. plurality of portions similarly 1 made andof the same generalconstruction'but and which can-:be readilynmanipulatedto provide changes.inuthe dimensions and size of'the electrode" whereby the..dischargecharacteristics of the electrode are. altered.

It is also an objectii'ofithe invention to provide improved apparatusfor making the electrodes of "the invention.

The manner. in which the above objects and other advantages of the'inventionmay be realized is set forth in the following detaileddescription illustrated by the'appended drawingsin which:

Fig. 1-. is-a: sectional view ofa complementary electrode structureincluding a discharge. electrode embodying theprinciples' of'theinvention;

Fig.2 is a'fragmentary view of a metalstrip incorporatedinthe dischargeelectrode ofFig. 1;

Fig. 3 is an cnlalrged detall 'view of a portion of the dischargeelectrode;

Fig. 4 is a sectionaliview taken along the line L4 of'Fig'. 3;

Fig. 5 is an elevational viewbf an alternative form of 1 precipitatingelectr'ode including discharge and nondischargeportions and embodying itheprinciples oftheinvention;

Figs; 6 and 7 are fragmentary elevation and sectional views respectivelyof a modified form 01 metal strip employed in making dischargeelectrodes Figs. 8 and: 9 are fragmentary elevation and sectional viewsrespectively of another-modified form of metal strip;

Fig. 10 is a plan view ofiapparatusfor winding the discharge electrodes;

ll, 12-and :13 are tenlare'ed detail views in side elevation of partsoftheapparatus shown inFig. l0; and

Fig. 14 is a further enlarged detail perspective semidiagrammatic viewof. a portion of the apparatus of Fig. 10 illustrating themanner inwhich the discharge prongs of the felectrodecare raised duringwinding.

Referring to the drawings, particularly to Fig. 1 thereof, the dischargeelectrode with which the invention is concerned is designated as aunitary structure by numeral 20? It has a base member 21 which may be atube, or a rod; a strip 22, including integrally rooted prong or pointedelements 23, which is wound helically around member 21 and fastened, asby tack welding, to member 2! at the ends 24, 24 of the strip andelsewhere along its length as may be desired; and means 25, usually atone end of the electrode only, for fastening the electrode to a suitablesupport. Such means may include a collar 28 fastened to base 2| aboutfive inches from the upper end of the base and a threaded end with nut2! at the extreme upper end of the base. The discharge electrode can befastened to such electrically insulated structures as are at presentused in electrical precipitators, but a deeper support such as the oneformed by angles 28, 28 separated by a sleeve 29 surrounding base member2|, has been found desirable, especially where the discharge electrodeis supported at one end only, yet must be held in a rigidly fixedposition, or in the center of tubular collecting electrode 38, forinstance. When the complementary electrodes are arranged as shown,electrode 20 is electrically connected to any conventional source ofhigh voltage current, such as that indicated diagrammatically at 3|, andcollecting electrode 38 is commonly connected to ground, as indicated at32.

The constructionof electrode 20 is shown in greater detail in Figs. 2, 3and 4. The base member 2| is shown as a metal tube of such diameter andwall thickness as may be necessary to provide the rigidit required.Tubes with diameters ranging from inch to 1. inch are generallysatisfactory, a tube inch outside diameter and having a wall thicknessof about inch being typical for electrodes from 3 to 7 feet long. Roundbars or bars of other cross section may be used but tubes are preferredfor several reasons, one being the facility a rather thin against thinstrips. The strip shown in Fig. 2 may be made of band iron, such as thatused to reinforce shipping containers, or may be made of strips shearedfrom sheets and welded end to end where strips of considerable lengthare needed.

The strip is slit or lanced at intervals along one side, as shown, theslits 33 being at an acute angle with the edge of the strip andextending from the edge to about the center of the strip. When such astrip is wound around a base member, themain body of the strip conformsto the surface of the base member but the discharge portions 23 do notbend; instead they stand out tangentially to the surface of base member2| as indicated at 23' in Fig. 4.

It is one object of the present invention to bend I these portions-theycommonly are bent along walled tube provides for tack welding are metwithin gaseous suspensions are not electrically charged equally ,wellunder the same conditions and it has been proposed to progressivelyalter the corona discharge and field strength characteristics of thetreating path through which the gases, from which suspended particlesare to be removed, flow. The electrode illustrated in Fig. 5 providessuch variable conditions. It is made up of two discharge sections 35 and36, a nondischarge sections 31, and a supporting member 30. Sections 35and 36 are both made in accordance with the teachings of the inventionbut section 35 is made to provide a stronger discharge and a weakeraverage electric field than section 36. These results are accomplishedby making prongs 4| longer and base tube 40 smaller in diameter insection 35 than the corresponding parts 42 and 43 respectively, insection 36. Prongs 4| can be altered in length by altering the length ofcuts 33, Fig. 2, and their number can be varied by changing thespacingbetween cuts. The farther a discharge point is positioned away from thebase member and from other points the more intense the discharge atconstant voltage and spacing between complementary electrodes. Section31 is shown in the form of a smooth collar. It may be formed from ashort tube by turning in the ends and it may be of larger diameter thanthe base members 49 and 43 because a shorter electrode-to-electrodespacing can be had without spark-over where the surfaces of thecomplementary electrodes are free from prongs or other surface portionsof small radius. No corona discharge is expected from member 31 butbecause of its large diameter and resulting proximity to a complementaryelectrode, as would be the case if it were positioned axially in thetubular electrode 30, Fig. 1, an electric field of very high averageintensity will terminate on its surface. This latter feature isadvantageous to provide a final cleaning of the gas in some types ofelectrical precipitators.

The composite electrode illustrated in Fig. 5 is made by first joiningthe base members 40 and 43 together, as by telescoping one into theother, and thereafter wrapping them with appropriate metal strips. Or,the base members can be wrapped first and assembled afterwards, which isto be preferred when a considerable number of electrodes are to be made.

Alternative forms of wrapping strips having integrally rooted dischargeelements are shown in Figs. 6 and 7 and Figs. 8 and 9. In Figs. 6 and 7,the strip 45 instead of having discharge points formed by making asingle cut in the edge of the strip has discharge points 46 defined by aV-shaped cut made near the center of the strip. The discharge points 48,in the modification shown in Figs. 8 and 9, are formed by perforating orpuncturing the strip 41 at spaced intervals with an instrument whichleaves the turned edges of the holes in a jagged condition.

Apparatus especially adapted for making the electrodes herein disclosedcan be variously constructed as to details and can be operated inconnection with other mechanisms, either mechanically or manuallyoperated, of various types.

Conveniently, an ordinary machinists lathe may be provided with novelattachments to adapt the same to the purposes of thepresent invention.In Fig. 10 there is shown, in plan view, a fragment of a machinistslathe including the bed runners 49 and 50, the usual carriage 5| that istranslatable along the bed runners. the usual cross slide 52 andcompound rest 53. These parts usual hand wheels and operating handles(not shown). As is also conventional, the carriage may be automaticallydriven by a lead screw at a preselectable rate proportional to the speedof rotation of the spindle that turns the work.

The attachments which are added to the lathe are (A) means for holdingthe lanced strip and feeding it, preferably under slight tension, at theproper angle upon the turning base member, here shown as a tube, (B) afollower rest for providing local support to the tube just in front ofthe strip as it is placed on the tube, and (C) means for contacting thepoints which project outwardly at a slight angle from the strip afterwinding and urging them to an upright, radial, position. Means C is notalways used. All three of these attachments are mounted on the crossslide of the carriage of the lathe and travel with it at the rate thewinding strip progresses along the tube. The strip holder A is placed onthe front or near end of the slide, being mounted on the compound toolrest 53 so that it can be turned at different angles. The follower restB and the point lifter C are mounted on the far end of the slide and canbe adjusted as to transverse position by turning the cross feed handwheel (not shown).

Strip holder A is shown in side elevation in Fig. 11, a portion of theside plate being broken away to show interior construction. It has abase 54 attached for instance by welds 55, to a body member 56. The base54 has open slots 51 for the entry of bolts by which it may be fastenedto compound rest 53. The body 56 is fiat on all sides except the topwhich has a trough-like depression 58 that extends from one side of thebody to the other, the width of the body being somewhat greater than thewidth of the strip to be wound. A complementary member 59 provides a topfor the body 56. It is flat on all sides except the bottom which is cutout with a trough-like depression El] and this depression forms withdepression 58, a small chamber, open at both sides, to be occupied byrolls GI and 62. A small slot 63 is cut in each end of top member 59 forthe entrance and egress of the strips to be guided by fixture A. Theslots are positioned to guide the strips under rolls 6| and over roll62, the relative position of the rolls causing the strip to bendslightly in passing through the fixture thus setting up a tension in thestrips. Flat side members 64 are fastened with bolts 65 to the sides ofmembers and 59 thereby holding them together and closing the sides ofchamber 5B, 66. Also, holes in side members [it provide bearings for thetrunnions 66 on the ends of rolls 6|, 62.

Follower rest B, shown in side elevation in Fig. 12, is made up of abase 57 with holes 68 for fastening means, and an upright member 69,rigidly attached to base 61, and in which a bearing 70 had been formedfor supporting base tubes 2| of electrodes during manufacture.

Fixture C, a right side view of which having parts broken away isillustrated in Fig. 13, has a base H on which an upright member 72 isrotatably mounted with a threaded fastening, to be looked in theposition and elevation desired by set screw it; an elbow shaped member14 rigidly fastened to upright member 12 and which in turn supports witha threaded fastening another e'bow shaped member 15, a set screw 16being provided to lock elbow member 15 in any desired position in elbowmember 14; a sleeve prongs 23.

member H, that is screwed intoelbow "I5and locked in desiredrotativeposition by set screw 13, having a cylindrical cavity 19 adapted toretain bearing means, for example, two needle bearings 88 separated by atubular spacer 8| and a thrust bearing comprising a single ball 82 inthe bottom of the cavity; a rotatable shaft83 one end of which ispositioned in cavity"|9 supported therein in bearings and against ball82 and the other end being fastened at right angles to a bar 84, andhaving a pin 85 projecting from the side thereof intermediate the endsand adapted for contact, against an abutment 86 on the end of member l1;and spring means 81 held in tension between an extension 88 on set screw78 and a fastening 89 on the far side of shaft 33, on the rear end ofbar 84, for instance.

Fig. 14 shows how the parts of fixture C are arranged to provide propercontact with prongs 23 to raise them during the winding operation.Telescoped members ll and 83 are inclined upwardly towards the junctionof members 83 and 84 at an angle of about 8 to 12 degrees with thehorizontal, and member 84 is inclined downwardly from the junction atabout the same angle with the horizontal. These angles are determinedafter suitable trials and are then held by tightening set screws 76 and18, respectively. Simultaneously, the height of bar member 8 4 and theangle with the axis of base member 2| at which it is most advantageouslyheld (about 12-15 degrees has been found satisfactory) is determined.This is done by raising and rotating member 72. The importance of theangle with the hor;zontal at which member 33 is held, or otherwisestated, the angle which the axis of rotation of yieldable shaft member83 makes with the plane of strip 22 as it approaches base 2|, is seenwhen it is recognized that the closer the angle is to 90 degrees thesooner bar member. 84 will slip off a discharge point 23 during erectionof the latter, causing rotation of shaft B3 in sleeve Tl as it does so.This relationship provides close control over the final position of Whena prong 23 first strikes lifting bar 84, upon rotation of base 2|, ittends to push the bar down and pin 85 is pushedagainst abutment 86. Asprong member 23 is lifted towards radial position, as shown in dottedlines in Fig. 14, the force on bar 84 changes in direction until, whenthe surface of prong 23 is at an angle some.- what less than 90 degreeswith the axis of rotation of shaft 83 it has an upward component whichlifts the end of bar 8 1 and lets it slip over the end of the prong.Spring 8"! immediately pulls the end of the bar down again, making itready to lift the next prong.

The apparatus is operated as follows: A strip of the width and thicknessdesiredis run through shears, not shown, which partially slit or lancethe strip to make, for instance, the cuts 33, Fig. 2. The lanced stripis then rolled on bobbins, or the like, of relatively large diameter.The end of the strip is put through fixture A and. attached under a jawof the lathe chuck when the chuck is tightened to grasp an end of a basemember 2|. A few turns of the strip are wound, the lathe turningclockwise (when facing the chuck). If it is desired that the edges ofthe strip touch as shown in Fig. 3, and they need not for the purposesof the invention, compound tool rest 53 is turned to and locked at theangle at which this result is realized. The cross slide 52 is set withthe follower rest B in contact with base member 2|, and the position offixture C is checkedin lathe chuck (not shown).

:the tube.

' accordance withthe relationships previously emphasized. The propergears to match the travel of the carriage with the speed of the spindletaking into account the width of the strip being wound have, of course,been determined and made available on the lathe. Winding can now proceeduntil the base member is completely covered with the pronged strip or tothe extent best suited to the purposes in mind. The strips havingdischarge points or prongs 1* can be attached to the supporting rods ortubes in various ways. The preferred way is by spot .welding. Inattaching the end of a strip to a tube which has been fastened in thewinding machine the end of the strip is passed through the guidemechanism A, which is to maintain the strip at the proper angle duringwinding, and made to contact the surface of the tube near the Theelectrode holding arm of an electric spot welder (such apparatus iswell-known to the art and is not shown) which is ordinarily back out ofthe way is pulled down upon the end of the strip and a small but secureweld is made attaching. the end of the strip to the far end of the stripand at intermediate points therealong.

It is not necessary, however, to use the welding machine during thewinding period. The starting end of the strip can be caught in the chuckwith the tube and in addition a simple retaining ringit may be a shortpiece of wire 9!} (Fig. 10). twisted tight with hand pliers-man be usedto fasten the strip to the tube, as a temporary fastening at least; asimilar fastening can be applied at the other end of the strip after theWinding operation has been completed. Wound tubes with such fasteningscan be placed in a rack as made and taken in lots to a welding machinewhich is advantageously used in conjunction with a specially designedholding frame which combination produces rapid, uniform, and permanentwelding of the strips to the tubes. Any temporary holding means, such asclasps or wire ties,

be a permanent part of the electrode assembly.

The wound strip after being suitably fastened along its contiguousedges, as by welding, may be withdrawn from the base member which hasserved as a mandrel in the winding operation, and when fitted with asuitable supporting attachment at one end thereof, may be used as adischarge electrode. lhis is particularly feasible for electrodes ofrelatively short length, but by selection of metal strip stock of properthickness and strength relatively long electrodes of adequate stiffnessmay be provided without the necessity for a coextensive base member.

It will be apparent that, particularly when a permanent base member ispart of the electrode construction the edges of the successive turns ofthe strip do not need to be in contact.

From the foregoing description it will be seen that the presentinvention provides an improved discharge electrode and process andapparatus for making the same, the electrode being characterized bydischarg points integrally rooted with a When the strip is wound on thetube to the extent desired, other welds are made at hellcallywoundconductive strip,- the strip preferably being wound upon a base member.It will also be appreciated that the process and apparatus of theinvention are extremely simple and provide desirable adjuncts to themanufacture of the electrode.

I claim:

l. A discharge electrode comprising an elongated base member, a metalstrip wound about said base member in a helix, and a plurality ofdischarge elements comprising projecting portions of said stripintegrally rooted with the helical portion thereof and formed byslitting the strip angularly inwardly from one edge thereof and bendingoutwardly the prong included between the slit and the edge of saidstrip.

2. A discharge electrode comprising an elongated base member, a metalstrip wound about said base member in a helix, and plurality ofdischarge elements comprising projecting portions of said stripintegrally rooted with the helical portion thereof and formed by makinga V-shaped slit through said strip and bending outwardly the prongincluded between the edges of said slit.

3. A discharge electrode comprising an elongated cylindrical basemember, a metallic sleeve positioned around the central portion of saidbase member, a nondischarging collar positioned around said base lnembernear one end thereof and adjacent to said sleeve, a. metal strip woundabout said base member in a helix extending from near the other end ofsaid base member to said sleeve, another metal strip wound about saidsleeve in a substantially contiguous helix and extending substantiallyfrom end to end of said sleeve, and a plurality of discharge elementscomprising pointed projecting portions of said strips integrally rootedwith the helical portions thereof.

4. Method of making a discharge electrode which comprises slitting ametal strip angularly inwardly from an edge thereof at spaced intervals,winding said strip upon an elongated base member in a helix, and bendingoutwardly the prongs included between said slits and the adjacent edgeportions of said strip.

5. Method of making a discharge electrode which comprises slitting ameta1 strip angularly inwardly from an edge thereof at spaced intervals,winding said strip upon an elongated base member in a helix, bendingoutwardl the prongs included between said slits and the adjacent edgeportions of said strip, and welding said strip to said base member.

6. Method of making a discharge electrode which comprises slitting ametal strip angularly inwardly from an edge thereof at spaced intervals,winding said strip upon an elongated cylindrical base member in a helix,and bending outwardly the prongs included between said slits and theadjacent edge portions of said strip.

7. Method of making a discharge electrode which comprises slitting ametal strip angularly inwardly from an edge thereof at spaced intervals,winding said strip upon an elongated cylindrical base member in a helix,bending outwardly the prongs included between said slits and theadjacent edge portions of said strip, and welding said strip to saidbase member. i

8. Apparatus for making a discharge electrode including a metal stripwound in a helix to form an elongated cylindrical member which comprisesmeans for mounting a cylindrical base element for rotation about itslongitudinal axis, means for rotating said base element, carriage meansmounted for translation parallel to the axis of said base element, meansfor translating said car=- riage at a rate proportional to the speed ofrotation of said base element, means mounted on said carriage forguiding a strip of metal having spaced slits defining integrally rooteddischarge prongs lying in the plane of the strip in Winding relation tosaid base element and for tensioning said metal strip as it is foundupon said base element, and additional means mounted upon said carriagemeans adjacent to the surface of the base element for engaging thedischarge prongs as the strip is wound upon the base element and raisingthe prongs to substantially radial position.

9. Apparatus for making a discharge electrode including a metal stripwound in a helix to form an elongated cylindrical member which comprisesmeans for mounting a cylindrical base element for rotation about itslongitudinal axis, means for rotating said base element, carriage meansmounted for translation parallel to the axis of said base element, meansfor translating said oarriage at a rate proportional to the speed ofrotation of said base element, means mounted on said carriage forguiding a strip of metal having spaced slits defining integrally rooteddischarge prongs lying in the plane of the strip in winding relation tosaid base element and for tensioning said metal strip as it is woundupon said base element, and additional means mounted upon said carriagemeans adjacent to the surface of the base element for engaging thedischarge prongs as the strip is wound upon the base element and raisingthe prongs to substantially radial position, said additional meanscomprising a bar yieldingly biased to rest position at an angle to theaxis of rotation of the base element and urged by said prongs out of thepath thereof when the latter have been raised to radial position.

10. A discharge electrode comprising an elongated base member, aconductive strip wound about said base member in a helix, and aplurality of discharge elements each comprising a projecting portion ofsaid strip formed by slitting the strip to define a prong extendinglongitudinally of the strip, said prong being integrally rooted to thestrip at the base of the prong, and bending the prong outwardly from thestrip.

11. Method of making a discharge electrode which comprises slitting ametal strip at spaced points therealong to form prongs extendinglongitudinally of the strip, said prongs being integrally rooted to thestrip at their bases, and winding said strip upon an elongated basemember in a helix having said prongs projecting therefrom.

ARCI HBALD F. MESTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 777,817 Stolp Dec. 20, 19041,067,974 Cottrell July 22, 1913 1,357,201 Nesbit Oct. 26, 19202,061,516 Frese Nov. 17, 1936 2,195,431 Shively et a1 Apr. 2, 19402,231,330 Gove Feb. 11, 1941 2,352,651 Meston July 4, 1944 FOREIGNPATENTS Number Country Date 299,476 Germany July 1.7, 1917 344,705Germany Nov. 28, 1921

